Songer, then 54, was alone in his Jacksonville home after a long day at work when he suddenly felt a searing pain — "like something hit me on the back of the head with a sledgehammer" — that radiated through his jaw, down his back and into his legs. He drove himself to the emergency room, announcing, "I think I'm having a heart attack."

A few hours later, a thoracic surgeon told Songer he had a 50-50 chance of surviving emergency open-heart surgery. The next day, Songer learned from his wife the name of the disorder that had caused his cardiac problem — along with several other maladies — which had gone undiagnosed for more than 50 years.

• • •

As a child, Songer was unusually tall and skinny, with severe buck teeth and weak wrists and ankles. Growing up in Florida in the 1960s and '70s, none of the doctors his parents consulted found anything to account for his weak muscles. At age 5 he underwent surgery for a double inguinal hernia, when soft tissue protrudes through weak abdominal muscles. For many people, hernia repair is a one-time fix; in Songer's case it would recur repeatedly as he got older.

By ninth grade, Songer's classmates nicknamed him "T-bone": he stood 6-2 and weighed about 110 pounds. He frequently sprained wrists and ankles. His lower back hurt.

In 2007, during his third hernia operation, the surgeon noted his poor abdominal muscle, advising him to eat more protein. Songer was puzzled: Although he had gained weight, his diet didn't seem different from that of his friends, none of whom had recurrent hernias. After his sixth hernia surgery in 2009, his doctor told him that losing weight — at 6-4 he was 228 pounds —would prevent future hernias.

That same year, Songer's blood pressure hit 140/90, and he was put on medicine to lower it.

At 51, Songer said, he felt decades older. "Every day I would wake up and think, 'I wonder what is wrong with me.' "

His doctors, he said, seemed perpetually rushed. "I don't think they had a clue," he said.

• • •

Then came the 2011 trip to the ER. Songer heard a radiology tech exclaiming, "Oh my God, look at that aorta!" and realized the man was talking about him.

A CT scan showed that Songer had suffered an extensive acute aortic dissection. This occurs when the body's largest blood vessel, which carries blood from the heart to the brain and other parts of the body, stretches or weakens, causing a tear that allows blood to leak.

Actor John Ritter, who became ill on a Hollywood set in 2003, died hours later of an aortic dissection at age 54. Treatment usually involves emergency surgery to repair or replace the aorta; the mortality rate within the first 48 hours is 50 percent.

"It's very dangerous," said Nathan R. Bates, the cardiothoracic surgeon who operated on Songer at Jacksonville's Memorial Hospital. Bates said he was fairly certain that the dissection was the result of Marfan syndrome: Songer's aortic root had the characteristic pear-shaped appearance seen in such patients, and he had the requisite body type: tall with spiderlike fingers and a narrow face.

The surgeon would have to replace the aortic valve with a mechanical valve and repair the tear with a Dacron graft.

The extent of Songer's dissection made surgery "a lot more complicated," Bates said. A portion of the tear that extended into his groin cannot be repaired and is being managed with medications, said Juzar Lokhandwala, his cardiologist.

When he learned he had a genetic disorder that doctors had missed for more than 50 years, Songer said he was both furious and relieved. His weak wrists and ankles, recurrent hernias and body type were all signs of Marfan syndrome. Episodes of neck pain followed by a headache were small tears that presaged the big dissection.

Marfan affects about 1 in 5,000 people worldwide; many have not been diagnosed. Medical historians have debated whether Abraham Lincoln it.

Songer's two children are undergoing genetic testing for the disorder.

"It really affects them," Songer said, because they are forbidden to play contact sports, which are deemed too risky for their hearts.

Marfan patients are given medicines to drive down their blood pressure; Songer monitors his several times a day.

"I feel like I've finally been given a GPS for my life," said Songer, who can no longer work. "I'm thankful to be alive and I'm grateful that Dr. Bates knew what was happening.''